This invention relates to improvements in or relating to accelerometers for use with vehicles and to vehicles having the accelerometers.
According to the invention there is provided an accelerometer which includes a means responsive to acceleration which provides an output signal in response to acceleration, and a signal presence detector associated therewith adapted to detect the continuous presence of an output signal from the acceleration responsive means for a predetermined time duration.
In this specification by "acceleration" is to be understood both positive and negative acceleration, i.e. acceleration and deceleration, unless otherwise indicated. Further, by accelerometer is meant a device or apparatus sensitive to acceleration.
The acceleration responsive means may be responsive to inertial forces and to linear or centripetal acceleration. The acceleration responsive means may be adapted to provide a digital output signal. Conveniently, it may be a binary, "on-off" device. The acceleration responsive means may be a pendulum, a mercury switch or a crystal transducer.
The presence detector may be variable such that the predetermined time duration may be varied.
The accelerometer may be electrically, magnetically, mechanically or hydraulically operable. The accelerometer is preferably electrically operable. Accordingly the acceleration responsive means may be adapted to provide an electrical output signal the presence detector being electrically operable.
In one embodiment, the acceleration responsive means may comprise an electrically conductive pendulum and a contact, the pendulum and the contact having electrical connection means with the pendulum being pivotable into contact with the contact, due to predetermined inertial accelerative force, to electrically bridge the connection means.
The presence detector may comprise an integrator and a level detector, the integrator being supplied from a voltage source via the pendulum and the contact. The integrator may conveniently be in the form of a series capacitive/resistive network, the level detector being set to detect a voltage level substantially less than the supply voltage. A discharge path for the capacitor is provided in this embodiment.
Recording means, responsive to the presence detector and adapted to record relevant particulars when the acceleration responsive means has been actuated for the predetermined time duration, may be provided. The recording means may for example be a counter for counting the number of times the acceleration responsive means is actuated for the predetermined time duration, or a timer for recording the aggregate amount of time in excess of the predetermined time duration that the acceleration responsive means is actuated. The accelerometer may for example be associated with an object in which case the recording means may be a camera, movie or still, for photographing the scene about the object.
Similarly, indicating means may be provided, the indicating means being responsive to the presence detector. These indicating means may be visually or audibly operable. They may for example be lamps, buzzers, loudspeakers, a hooter, etc.
The accelerometer may further include disabling means, responsive to the presence detector, for rendering the recording and/or indicating means insensitive to actuation by the response means for a predetermined time duration after the presence detector has detected an actuation of the acceleration responsive means. Accordingly, if the acceleration responsive means is sufficiently actuated a number of times during this disabled period, the recording means or indicating means will only record or indicate one actuation. The disabling means may include a ramp generator and a level detector arranged to form a time base. Alternatively, electronic digital techniques may be utilized, e.g., by means of a monostable multi-vibrator. The disabled time duration may also be variable.
Analogue or digital electronic techniques may also be utilized for the presence detector or other elements. Similarly discrete components or integrated circuit components may be utilized.
In order to test whether the accelerometer is operating correctly a test means may be included. The test means may be operatively connected to the presence detector to actuate the presence detector by providing it with a simulated signal from the acceleration responsive means. The test means may also be interconnected with any recording and/or indicating means to disable them when the operation of the accelerometer is being tested. Thereby test signals supplied to the presence detector are not recorded or indicated as being true actuations of the acceleration responsive means. The test means may further be lockable so that only authorized persons can test the accelerometer.
The acceleration responsive means may be further adapted to provide one of a number of output signals dependent on the character of the acceleration. For example, the output signals may be dependent on the quantized amplitude of the acceleration or on the direction of the acceleration. In one embodiment the acceleration responsive means may be electrically operable and comprise a pendulum and a plurality of contacts. The contacts may be arranged to be successively contacted as the pivotal angle of the pendulum increases to be responsive to the amplitude of the acceleration; or they may be disposed in a plane about the pendulum to be responsive to the direction of the acceleration. Alternatively, in another embodiment, a plurality of acceleration responsive elements, such as pendulums, may be utilized, each of the elements being responsive to acceleration of a predetermined magnitude or direction.
With such acceleration responsive means, a plurality of presence detectors may be provided, one for each of the output signals of the acceleration responsive means. Similarily, a plurality of recording means and/or indicating means may be provided, each being responsive to one of the presence detectors. By this means the magnitude of the acceleration responded to by the acceleration responsive means, or its directions, may be independently recorded and/or indicated.
The accelerometer may have mounting means for mounting it in a vehicle, particularly a motor vehicle. The connecting means may have electrical connection means for electrically connecting the accelerometer to control apparatus and/or operating elements of the vehicle. For example, the accelerometer may have its own power source, or it may be connectable to a source of electrical power, such as an accumulator in the vehicle; or the accelerometer may be interconnected with the windscreen wipers or headlamps of the vehicle to render the acceleration responsive means or the presence detector more sensitive.
The accelerometer's components may conveniently be housed in a tamper-proof sealed housing. The accelerometer may be self-sufficient or it may be removable receivable in a bracket which is mountable in a vehicle and connectable by suitable connecting means to elements of the vehicle.
The accelerometer may have a region, e.g., on the housing, on which a datum reference value may be recorded. This datum reference value may for example be the odometer reading of the vehicle or the date of installation, or the date of initial use, of the accelerometer.
An accelerometer for use with a vehicle may further have instructions to the driver exhorting and explaining to him how to drive safely.
The invention further provides a vehicle having an accelerometer according to the invention.